>
> >I do not understand why OA would damage mites but not bees.  Can 
> >anyone
> explain?


This is a good question, and a couple of possible answers come to mind:

1.  That it is simply a matter of surface to body mass ratio--a varroa mite has far more surface relative to body mass than does a bee.  This explanation assumes that the OA is absorbed over the entire body surface, which is apparently dependent upon humidity, as well as any humectants added to the OA.

2.  That the mite's sticky tarsal pad is more prone towards absorption than is a bee's arolium (http://www.pnas.org/content/98/11/6215.full.pdf).  And this may also relate to (1) above, since the arolium: body mass ratio of a mite would be greater than that of a bee.  A question is whether the bees, when walking on comb, predominately use their tarsal claws, or whether they extend their arolia.



I am rerunning that test with more mites and a bit of planning.   I am having a bit of difficulty finding enough mites though!  Some season it seems weather is involved and mites drop to low levels on their own.  Seems this year is one.  Even my untreated hives are showing 1-3 per 300  which makes finding phoretics very tricky.

I am very sure at the moment that absorption thru Tarsal pads is a definite route,  I will play a bit with absorption on the surface of the carapaces,  anywhere on the underside is about impossible to place.   If you have never tried it,  mites are very active and touching them elicits a reaction like putting a cat in water. ( a 6 legged cat)   Yes  I am aware mite have 8 legs,  but interesting enough it seems they don't use the front 2 for mobility or handling.   

As mentioned I haven’t been able to find the numbers I want yet (about 30 needed for a baseline)  but on a sample of 4 left to handle OA  it seems 5 minutes of handling of a OA crystal brings on death in about 6 hours.   I have been very careful to watch them and at no time do they put it in their mouthparts,  or transfer to the mouth.  It seems mites are not like bees in that respect as I have seem no grooming behavior or anything similar using mouthparts or even the front 2 legs,  which are also equipped with the "sticky tarsal pad"


Charles

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